Transplantation immunity to transplacentally induced mouse lung tumors is related to a cross-reactive antigen present on many lung tumors of strains C3Hf, C57BL/6 and DBA/2 mice. Genetic control of antigen expression is closely linked to the H-2 histocompatibility locus. The role, if any, of this antigen in genetic control of susceptibility and resistance to lung tumors in mice, and its potential exploitability for immunotherapy and immunoprophylaxis of such tumors, is under study. BIBLIOGRAPHIC REFERENCES: Martin, W. John, Gipson, Thomas G., and Rice, Jerry M.: H-2a-associated alloantigen expressed by several transplacentally-induced lung tumors of C3Hf mice. Nature 265: 738-739, 1977. Martin, W.J., Gipson, T.G., Martin, S.E., and Rice, J.M.: Depressed alloantigen on transplacentally induced lung tumor coded for by H-2 linked gene. Science 194: 532-533, 1976.